From 6b45e0f81267be6140f0f178579494ca6d24443b Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Mon, 31 Oct 2022 19:55:32 -0700
Subject: Restructure a lot of the control registers

---
 isa/decode.cpp | 45 ++++++++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 17 deletions(-)

(limited to 'isa/decode.cpp')

diff --git a/isa/decode.cpp b/isa/decode.cpp
index 1496364..201a684 100644
--- a/isa/decode.cpp
+++ b/isa/decode.cpp
@@ -1,12 +1,18 @@
 #include <cassert>
+#include <cstdint>
 #include <iostream>
 
 #include "isa/isa.h"
 
-instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bits, bool interrupt)
+instruction_context decode(std::uint_fast32_t flags, unsigned int pc, unsigned int bits, bool interrupt)
 {
-    auto df = dfifb >> 3;
-    auto ifb = dfifb & 00007;
+    //bool gt = (flags >> 10) & 1;
+    //bool ir = (flags >> 9) & 1;
+    //bool ii = (flags >> 8) & 1;
+    //bool ie = (flags >> 7) & 1;
+    //bool u = (flags >> 6) & 1;
+    bool ifb = (flags >> 3) & 7;
+    bool df = flags & 7;
 
     instruction_context inst;
     inst.next_pc = (pc & ~07777) | ((pc + 1) & 07777);
@@ -16,6 +22,7 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
         assert(df == 0);
         assert(ifb == 0);
         inst.next_pc = pc;
+        pc = 0;
     }
 
     switch (bits >> 9) {
@@ -79,42 +86,46 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
                     switch (bits & 07) {
                         case 0:
                             // SKON skip if interrupts enabled
-                            inst.read_ctlreg = INT_ENABLE;
+                            inst.read_ctlreg = FLAGS;
                             inst.possibly_redirects = true;
                             inst.ef = [](auto &ctx) {
-                                if (ctx.ctlval.value() & 1)
+                                if (ctx.ctlval.value() & FLAG_INT_ENABLE)
                                     ctx.next_pc = (ctx.next_pc & 07777) | ((ctx.next_pc + 1) & 07777);
                             };
                             break;
                         case 1:
                             // ION set int_enable_delay
-                            inst.read_ctlreg = INT_ENABLE;
-                            inst.write_ctlreg = INT_ENABLE;
+                            inst.read_ctlreg = FLAGS;
+                            inst.write_ctlreg = FLAGS;
                             inst.ef = [](auto &ctx) {
-                                ctx.ctlval.value() |= 2;
+                                ctx.ctlval.value() |= FLAG_INT_ENABLE_DELAY;
                             };
                             break;
                         case 2:
                             // IOFF clear int_enable and int_enable_delay
-                            inst.write_ctlreg = INT_ENABLE;
+                            inst.read_ctlreg = FLAGS;
+                            inst.write_ctlreg = FLAGS;
                             inst.ef = [](auto &ctx) {
-                                ctx.ctlval = 0;
+                                ctx.ctlval.value() &= ~FLAG_INT_ENABLE_DELAY & ~FLAG_INT_ENABLE;
                             };
                             break;
                         case 3:
                             // SRQ skip if pending interrupt
-                            inst.read_ctlreg = INT_PENDING;
+                            inst.read_ctlreg = FLAGS;
                             inst.possibly_redirects = true;
                             inst.ef = [](auto &ctx) {
-                                if (ctx.ctlval.value())
+                                if (ctx.ctlval.value() & FLAG_INT_REQUEST)
                                     ctx.next_pc = (ctx.next_pc & 07777) | ((ctx.next_pc + 1) & 07777);
                             };
                             break;
                         case 4:
                             // GTF get flags
+                            inst.read_ctlreg = FLAGS;
+                            inst.need_read_link = true;
                             inst.ef = [](auto &ctx) {
-                                std::cerr << "unimplemented GTF\n";
-                                assert(false);
+                                auto flags = ctx.ctlval.value();
+                                flags |= (unsigned int)ctx.link.value() << 11;
+                                ctx.acc = flags;
                             };
                             break;
                         case 5:
@@ -153,11 +164,11 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
                             };
                             break;
                         case 5:
-                            // KIE set TT_INT_ENABLE to the low bit of the accumulator
+                            // KIE set TT_FLAGS from the accumulator
                             inst.need_read_acc = true;
-                            inst.write_ctlreg = TT_INT_ENABLE;
+                            inst.write_ctlreg = TT_FLAGS;
                             inst.ef = [](auto &ctx) {
-                                ctx.ctlval = ctx.acc.value() & 3;
+                                ctx.ctlval = ctx.acc.value();
                             };
                             break;
                         case 6:
-- 
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